Catalytic hydrocracking process

ABSTRACT

In a process wherein jet fuels and gasoline are produced from hydrocarbons boiling in the range 300* to 1,500* F., including substantial quantities of hydrocarbons boiling in the range 300* to 650* F. and substantial quantities of heavier hydrocarbons boiling in the range 550* to 1,100* F., by process steps including catalytic hydrocracking, the improvement which comprises catalytically hydrocracking said hydrocarbons boiling in the range 550* to 1,100* F., and catalytically hydrogenating said hydrocarbons boiling in the range 300* to 650* F. prior to making use of said hydrocarbons boiling in the range 300* F. to 650* F. for jet fuel or for hydrocracking feedstock.

United States Patent Inventor James R. Kittrell [56} References Cited ElCermor Cfllf- UNITED STATES PATENTS g 232 1 3,166,489 1/1965 Mason etal.208/57 Patented Nov. 2, 1971 3,240,694 3/1966 Mason ct al. 208/59Assignee Chevron Research Company Primary Examiner- Delbert E. Gantz SanFrancisco, Calif. Assistant ExaminerG. E. Schmitkons Attorneys-A. L.Snow, F. E. Johnston, C. J. Tonkin and Roy H. Davies ABSTRACT: Inaprocess wherein jet fuels and gasoline are produced from hydrocarbonsboiling in the range 300 to 1.500" F., including substantial quantitiesof hydrocarbons fgfifl if PROCESS boiling in the range 300 to 650 F. andsubstantial quantities Of heavier hydrocarbons boiling in the range 550to 1.100" F., U.S.Cl 208/80, by process steps including catalytichydrocracking. the im- 208/57, 208/89, 208/93, 208/108. 208/l l l,provement which comprises catalytically hydrocracking said 260/667hydrocarbons boiling in the range 550 to l,l00 F., and cata- Int. ClClflglJ/Qg, lytically hydrogenating said hydrocarbons boiling in therange Cl0g 23/00, ClOg 37/06 300 to 650 F. prior to making use of saidhydrocarbons boil- Field of Search 208/80, 89, ing in the range 300 F.to 650 F.v for jet fuel or for 57 hydrocracking feedstock.

I 1 15 IS IS 300M600 HYDROGENATION 0 o AROMATICS w 20 H2 22 GASOLINE w 1j 0 Q} HYDROFINING HYDROCRACKING J 2r 300-600F. 1.! 5 6 a 6 2s CATALYTICHYDROCRACKING PROCESS INTRODUCTION PRIOR ART The production of jet fuelfrom hydrocarbon feedstocks by various combinations of processing steps,including catalytic hydrocracking, is well known. Certain of thesecombinations of processing steps are disclosed in U.S. Pats. Nos.3,172,833, 3,172,839 and 3,240,694. However, there are certain remainingproblems in the production of jet fuel by process steps, includingcatalytic hydrocracking, for which the prior art has not yet providedsolutions. The process of the present invention provides a solution tocertain of these problems, including the one which now will bediscussed.

In a petroleum refinery in which jet fuel is being produced by processsteps, including catalytic hydrocracking, there are two primary sourcesof hydrocarbon feedstock for the catalytic hydrocracking zone: (I)hydrocarbons boiling in the range 550 F. to l,l F., which are to behydrocracked to produce a jet fuel boiling in the range 300' to 650 F.,which jet fuel is termed synthetic" to the extent that it boils belowthe boiling range of the hydrocarbon feedstock; and (2) hydrocarbonsboiling in the range 300 to 650 F., for example cycle oils or coker gasoils. Almost invariably, the more synthetic the jet fuel, the higher itssmoke point and the lower its freeze point. However, it is obvious thatthe 300 to 650 F. boiling range hydrocarbons cannot be converted inlarge proportion in a hydrocracking zone to synthetic jet fuel.

Nevertheless, efforts have been made to include such 300 to 650 F.boiling range materials in the feed to the hydrocracking zone, in thehope that, while such materials cannot be converted in large proportionto synthetic jet fuel, nevertheless they might be upgraded for jet fueluses, for example by saturating the aromatics contained therein. Resultsof these efforts have been extremely poor; not only were thesehydrocarbons not convertible in the hydrocracking zone in largeproportion to synthetic materials, but in the hydrocracking zone they:(a) were not significantly upgraded for jet fuel uses, that is, thearomatics therein were not substantially saturated, because the presenceof heavier hydrocarbons boiling in the 550 to l,l00 F. range suppressedthe desired aromatics saturation reaction; and (b) the quality of thetotal jet fuel being produced in the hydrocracking zone wassubstantially lower than the quality of the jet fuel that could beproduced therein by hydrocracking 550 to l,l00 F. boiling rangehydrocarbons in the absence of lighter 300 to 650 F. boiling rangehydrocarbons.

OBJECTS In view of the foregoing, it is an object of the presentinvention to provide a hydrocarbon conversion process, including acatalytic hydrocracking step, capable of producing high yields ofvaluable fuel products, including jet fuels, from hydrocarbon feedstocksboiling in the range 300 to l,l00 F. and containing substantialquantities of materials boiling in the range 300 to 650 F. andsubstantial quantities of heavier materials boiling in the range 550 tol,l00 F. It is a more specific object of the present invention toprovide a hydrocarbon conversion process. including a catalytichydrocracking step, which will upgrade the hydrocarbons boiling in therange 300 to 650 F. while at the same time avoiding any adverse effectof such hydrocarbons on the production of jet fuel from heavier 550 tol,l00 F. boiling range hydrocarbons by catalytic hydrocracking.

DRAWlNG The present invention will best be understood, and furtherobjects and advantages thereof will be apparent, from the followingdescription when read in connection with the accompanying drawing.

The drawing is a schematic illustration of apparatus and flow pathssuitable for carrying out the process of the present invention.

STATEMENT OF INVENTION In accordance with the present invention, it hasbeen found that: (l) in hydrocarbon materials boiling in the range 300to l,l00 F. and containing substantial quantities of materials boilingin the range 300 to 650 F. and substantial quantities of heaviermaterials boiling in the range 550 to 1 F., preponderant quantites ofthe aromatic compounds are concentrated in the materials boiling in therange 300 to 650 F accordingly, not only is it impossible to convertthese materials in large proportion to synthetic jet fuels by catalytichydrocracking, but jet fuels produced from these materials in acatalytic hydrocracking step have undesirably high aromaticity and lowsmoke point, unless a substantial amount of aromatics saturation takesplace in the hydrocracking reaction zone; and (2) a substantial amountof aromatics in the 300 to 650 F. boiling range hydrocarbons supplied toa hydrocracking reaction zone are not saturated during the hydrocrackingreaction when the hydrocarbon feed in the hydrocracking reaction zoneincludes substantial quantities of heavier hydrocarbons boiling in therange 550 to l,l00 F the presence of the heavier hydrocarbons inhibitssaturation of the aromatics contained in the 300 to 650 boiling rangematerials.

In accordance with the present invention there is provided, in a processwherein at least one hydrocarbon feedstock containing substantialquantities of materials boiling in the range 300 to 650 F. andsubstantial quantities of heavier materials boiling in the range 550 tol,l00 F. is converted to valuable products including gasoline and jetfuel by process steps including catalytic hydrocracking in ahydrocracking zone, the improvement which comprises catalyticallyhydrocracking in said zone said materials boiling in the range 550 tol,l00 F., catalytically hydrogenating in a second reaction zone saidmaterials boiling in the range 300 to 650 F and withdrawing valuablefuel products from each of said zones.

Further in accordance with the present invention, said materials boilingin the range 600 to l,l00 F. may be catalytically hydrofined prior tobeing catalytically hydrocracked.

Further in accordance with the present invention, the liquid effluentfrom said second reaction zone may be combined with effluent materialsfrom said hydrocracking reaction zone boiling in the range 300 to 650 F.to produce a superior jet fuel.

Still further in accordance with the present invention, at least aportion of the effluent from said second reaction zone may becatalytically hydrocracked in said hydrocracking reaction zone.

HYDROCARBON FEEDSTOC KS Hydrocarbon feedstocks suitable for use in theprocess of the present invention boil in the range 300 to l,l00 F. andcontain substantial quantities of materials boiling in the range 300 to650 F. and substantial quantities of heavier materials boiling in therange 550 to l,l00 F. The feedstocks preferably boil over a range of atleast 50 F. within each of the aforesaid boiling ranges. Suitablefeedstocks include those heavy distillates normally defined as heavystraight run gas oils and heavy cracked cycle oils, as well asconventional FCC feeds and portions thereof. Cracked stocks may beobtained from thermal or catalytic cracking of various stocks, includingthose obtained from petroleum. gilsonite, shale and coal tar. Feedstocksmay contain nitrogen and sulfur. in amounts usually associated with thefeedstocks previously described.

The materials boiling in the range 300 to 650 F. will contain at least20 volume percent aromatics.

The materials boiling in the range 300 to 650 F. may have been separate,at all times prior to being processed in accordance with the presentinvention, from the materials boiling in the range 550 to 1,100 F.Alternatively, the materials boiling in" the range 300 to 650 F. may beseparated from a hydrocarbon stock containing both these materials andhigher boiling materials. by separation at a cut point in the range 550to 650 F. It also will be understood that a jet fuel will boil in therange 300 to 650 F., but more preferably in the range 300 to 600 F., andstill more preferably in the range 300 to 550 F. In accordance with theforegoing, it further will be understood that: (a) the hydrocarbon feedsupplied to the hydrocracking zone in the process of the presentinvention may have an initial boiling point as low as 550 F. and as highas 650 F.; and (b) to the extent that the jet fuel fraction separatedfrom the hydrocracking zone effluent boils below the initial boilingpoint of the hydrocracking zone hydro carbon feed, the jet fuel in thatfraction will be synthetic.

AROMATICS HYDROGENATION STEP The aromatics hydrogenation step in theprocess of the present invention is conducted in a hydrogenation zoneoperated at conventional aromatics hydrogenation conditions, includingtemperatures in the range 300 to 700 F preferably 400 to 650 F.,pressures of at least 300 p.s.i.g., and liquid hourly space velocitiesof 0.3 to 5.0, effective to saturate a substantial portion, preferablyat least 50 volume percent, of the aromatics present in the hydrocarbonfeed to the hydrogenation zone. Hydrogen is supplied to thehydrogenation zone at a rate at least sufficient to effect the desiredsaturation, preferably at the rate of at least 1,000 s.c.f. of hydrogenper barrel of hydrocarbon feed, and more preferably at, least 2,000s.c.f. of hydrogen per barrel of hydrocarbon feed.

The catalyst used in the hydrogenation zone may be any conventionalaromatics hydrogenation catalyst, for example platinum or palladium orcompounds thereof on alumina or other carrier having low crackingactivity and high surface area. When the hydrocarbon feedstock to thehydrogenation zone contains substantial amounts of sulfur, a platinumorpalladium-containing catalyst will be found less desirable than aconventional sulfur resistant hydrogenation catalyst, for example onecomprising an alumina support together with molybdenum or tungsten andnickel or cobalt hydrogenation components. The hydrogenation componentsmay be present in the catalyst in the sulfide or oxide form. The GroupV] com-. ponent content of the catalyst may be to 25 weight percentexpressed as metal, and the Group VIII component content of the catalystmay be 1 to 20 weight percent expressed as metal.

The aromatics hydrogenation step should be so conducted that less than 5percent cracking of the hydrocarbon feedstock thereto occurs therein,particularly when it is desired to operate the process of the presentinvention for production of maximum amounts of jet fuel.

H Y DROFIN ING STEP The hydrofining step in the process of the presentinvention may be conducted in the hydrotiningv zone operated atconventional hydrofining conditions, including temperatures in the range450 to 850 F preferably 550 to 800 F., pressures of at least 300p.s.i.g., and liquid hourly space velocities of 0.3 to 5.0. Hydrogen issupplied to the hydrotining zone at the rate of 1,000 to 15,000 s.c.f.of hydrogen per barrel of hydrocarbon feed supplied to that zone. Thehydrotining catalyst may be a conventional sulfur-resistant hydrofiningcatalyst, for example one comprising an alumina support together withmolybdenum or tungsten and nickel or cobalt hydrogenation components.The hydrogenation components may be present in the catalystin thesulfide or oxide form. The Group V! component content of the catalystmay be 5 to 25 weight percent expressed as metal, and the Group VIIIcomponent content of the catalyst may be 1 to 20 weight percentexpressed as metal.

HYDROCRACKING STEP The hydrocracking step in the process of the presentinvention is conducted in a hydrocracking zone operated at conventionalhydrocracking conditions, including temperatures in the range 400 to 900F preferably 500 to 800 F pressures of at least 300 p.s.i.g., preferably1,500 to 3,500 p.s.i.g., and liquid hourly space velocities of 0.3 to5.0. Hydrogen is supplied to the hydrocracking zone at the rate of 1,000to 20,000 s.c.f. of hydrogen per barrel of hydrocarbon feed supplied tothat zone.

The catalyst used in the hydrocracking zone may be any conventionalhydrocracking catalyst, for example nickel sulfide on silica-alumina. Ahydrocracking catalyst comprising a crystalline zeolitic molecular sievedispersed in a matrix of other catalyst components, which may includenickel, tungsten and silica alumina, will be especially suitable.

The hydrocracking zone preferably will be operated at a substantiallyconstant conversion of at least 25 volume percent, preferably 35 tovolume percent, per pass, of the hydrocarbon feed to products boilingbelow the initial boiling point of that feed.

DESCRIPTION OF PROCESS OPERATION WITH REFERENCE TO DRAWING Referring nowto the drawing, there shown is an exemplary overall process flow diagramsuitable for carrying out the process of the present invention. Ahydrocarbon feedstock boiling in the range 300 to 600 F., containing atleast 20 volume percent aromatics, is passed through line I tohydrogenation zone 2. A hydrocarbon feedstock boiling in the range 600to 1,100' F. is passed through lines 3 and 4 to hydrofining zone 5 or,alternatively, through lines 3, 6 and 7 to hydrocracking zone 8.

The hydrocarbon feedstocks in lines 1 and 3 may be from separate sourcesor, as shown in the drawing, may be fractions obtained from a singlehydrocarbon feedstock. In the drawing, a hydrocarbon feedstock boilingin the range 300 to l,500 F. is passed through line 10 into distillationcolumn 11 and separated into fractions, including the 300 to 600 F.fraction withdrawn through line 1 and the 600 to l,l00 F. fractionwithdrawn through line 3. From distillation column 11 light ends areremoved through line 12 and l,lO0 F." materials are removed through line13.

In hydrogenation zone 2, the hydrocarbon feedstock thereto ishydrogenated at conditions previously described in the presence ofhydrogen supplied to zone 2 through line [4. The liquid effluent fromzone 2 is recovered as a product through line 15. Alternatively, all ora portion of the liquid effluent from zone 2 may be passed through line16 to hydrocracking zone 8. All or a portion of the material in line 16may be passed through lines 17 and 4 to hydrofining zone 5 Any feedstocksupplied through line 4 to hydrofining zone 5 is hydrofined in that zoneunder conditions previously described in the presence of a catalyst aspreviously described and in the presence of hydrogen supplied to zone 5through line 18. The liquid effluent from hydrofining zone 5 is passedthrough line 7 to hydrocracking zone 8.

The hydrocarbon materials supplied through line 7 to hydrocracking zone8 are hydrocracked in that zone at conditions previously described inthe presence of a catalyst as previously described and in the presenceof hydrogen supplied to zone 8 through line 20. The effluent from zone 8is passed through line 21 to distillation column 22, where it isseparated into fractions, including a gasoline fraction which iswithdrawn through line 23 and a fraction lighter than gasoline which iswithdrawn through line 24. From distillation column 22 a fractionboiling in the range 300 to 600 F. is passed through line 25 and blendedwith the materials in line 15 to form a superior jet fuel product. Fromdistillation column 22, a fraction boiling above 600 F. is recycledthrough lines 26, 6 and 7 to hydrocracking zone 8.

Although only specific embodiments of the present invention have beendescribed, numerous variations can be made in these embodiments withoutdeparting from the spirit of the invention and all such variations whichfall within the scope of the appended claims are intended to be embracedthereby.

What is claimed is:

1. In a process wherein an unhydrofined hydrocarbon feedstock containingnitrogen and sulfur in amounts usually associated with said feedstock,said hydrocarbon feedstock containing substantial quantities ofmaterials boiling in the range 300 to 650 F. and substantial quantitiesof heavier materials boiling in the range 550 to l,l00 F. is convertedto valuable products including gasoline and jet fuel by process stepsincluding catalytic hydrocracking in a hydrocracking reaction zone, theimprovement which comprises separating said unhydrofined feedstock intoa first portion predominantly comprising said materials boiling in therange 550 to l,l00 F. and a second portion predominantly comprising saidmaterials boiling in the range 300 to 650 F., catalyticallyhydrocracking said first portion in said hydrocracking reaction zone ata temperature in the range 400 to 900 F. a pressure of at least 300p.s.i.g., and a liquid hourly space velocity in the range 0.3 to 5.0, ata hydrogen supply rate of l,000 to 20,000 s.c.f. of hydrogen per barrelof said materials boiling in the range 550' to 1,100" F., catalyticallyhydrogenating said second portion in a second reaction zone at atemperature in the range 300 to 700 F., a pressure of at least 300p.s.i.g., a liquid hourly space velocity of 0.3 to 5.0 and a hydrogensupply rate of at least 1,000 s.c.f. of hydrogen per barrel of saidmaterials boiling in the range 300 to 650 F., to the extent that atleast 50 volume percent of the aromatics present in the hydrocarbon feedto said second reaction zone are saturated, separating a fractionboiling in the range 300 to 650 F. from the effluent from saidhydrocracking reaction zone, and combining, without further processing,the effluent from said second reaction zone with the said fractionboiling in the range 300" to 650 F. separated from said hydrocrackingreaction zone effluent, to produce a jet fuel product.

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